RF power transmitters with high power efficiency and linearity: architectures and linearization by digital predistortion

Power Amplifiers (PA) are critical elements of radiocommunication systems because their power efficiency conditions the autonomy and cost of equipments and their linearity influences on performance of the communication. With the emergence of 5G systems, achieving a good trade-off between linearity and efficiency is becoming more crucial. New post-OFDM waveforms are proposed for 5G networks in order to improve spectral occupancy, decrease latency and facilitate asynchronous communications. However, these waveforms exhibit very high crest factors and are very sensitive to the PA non-linearities. Morever, carrier aggregation allows for very high data rate but creates new challenges for transmitters in terms of bandwidth, intermodulation, harmonics and filtering.

In that context, the presentation will be dedicated to architectures and linearization techniques for high efficiency linear transmitters.
After a short discussion on the impact of the evolution of communication systems and standards on transmitter architectures, it will give an overview of the architectures of power transmitters (Doherty, Envelop tracking, sampled architectures …) in the context of 3G/4G/5G systems. Then it will focuss on linearization by digital predistortion: basic principles and challenges.